Ultrasound imaging is a medical imaging technique for imaging organs and soft tissues in a human body. Ultrasound imaging uses real time, non-invasive high frequency sound waves to produce a two-dimensional (2D) image and/or a three-dimensional (3D) image.
In ultrasound imaging, speckle noise occurs as a result of interference of scattered echo signals reflected from an object, such as an organ. The speckle noise or speckle appears as a granular grayscale pattern on an image. The speckle noise degrades image quality and increases the difficulty of discriminating fine details in images during diagnostic examinations. Speckle noise may degrade image quality since the speckles obtained from different angles are incoherent,
Some ultrasound systems are capable of spatially compounding a plurality of ultrasound images of a given target into a compound image. The term “compounding” generally refers to non-coherently combining multiple data sets to create a new single data set. The plurality of data sets may each be obtained from imaging the object from different angles, using different imaging properties, such as, for example, aperture and/or frequency, and/or imaging nearby objects (such as slightly out of the plane steering). These compounding techniques may be used independently or in combination to reduce speckle and improve image quality.
In conventional ultrasound imaging, the image is acquired by a series of scan lines. This results in an image in which some anatomical structures may be “shadowed” by objects closer to the transducer whose stronger reflections have drained the beam energy along that scan line. This may be referred to as shadowing. Moreover, dense diagonal structures may not be optimally imaged as they will tend to reflect energy in other directions than back to the transducer. Typically, when the boundaries of anatomical structures are parallel to the ultrasonic transducer, the acoustic waves reflect directly back to the ultrasonic transducer with less dispersion and a clear image is obtained. However, diagonal or vertical structures are sub-optimally imaged using conventional ultrasound because of the lower percentage of acoustic energy that reflects back to the ultrasonic transducer. Furthermore, structures that are hidden beneath strong reflectors are also sub-optimally imaged.
A plurality of data sets or compound frames imaging the same target but under different conditions may be combined to generate a single view or compound image by combining the data received from each point in the compound image target that has been received from each compound frame. An ultrasonic transducer array may be utilized to implement the difference in the conditions under which the individual component data is acquired by means of electronic beam steering and/or electronic translation of the component frames. The component frames are combined into a compound image by summation, averaging, peak detection, or other combinational means. The compounded image may display reduced speckle pattern and enhanced specular reflector delineation than a non-compounded ultrasound image, which serves to emphasize structural information in the image.
Visualizing anatomical features of organs such as anomalies in the heart walls, and in particular the coronary apparatus, may be occluded by the fact that a given frame of ultrasound data insonifies an anatomical region from only one particular angle since the degree of backscattering may be very angle dependent, as are effects like shadowing and reverberation from surrounding structures and deflection of energy from the inclination of the structure itself, all effects that contribute to masking such features out. The image quality of such features could also suffer from a poor signal/noise ratio or low contrast to the surroundings. They may be difficult to visually identify because of their changing location and appearance from frame to frame because of the heart motion. Moreover the resolution needed to see such structures could be compromised by high frame rate demands generally posed in 3D cardiac imaging in order to capture the heart dynamics.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.